The journey of NASA's Cassini spacecraft around Saturn is coming to an end. The Cassini mission has been exploring the Saturn system for nearly 13 years and has rewritten the textbooks on the ringed planet and its moons, but the spacecraft is pretty much out of fuel. However, a lot of work from engineers designed the spacecraft and programmed its flight path, and they used astrodynamics to navigate the spacecraft between the rings of the planet. Part of the "Crazy Engineering" series.